This invention relates to a method for recovering oil from an oil bearing strata by means of the generation of shock waves and ultrasonic waves in a liquid in the bearing earth strata.
As used in this specification, the term "oil" means natural oil or petroleum as found in nature particularly in oil bearing earth formations. Such a product is often called "crude oil" which consists principally of hydrocarbons.
The removal of oil by the use of drilled oil wells in the oil bearing formation has been practiced for several generations. Many of the wells have ceased to be utilized because it is not economical to remove by conventional methods the oil which remains in the formation. To remove the oil which is left behind, such oil being called "residual oil", it has been suggested to use various techniques. The primary technique is to flood the well with water in order to induce further flow. In addition to water flooding, other techniques have been developed such as the injection of liquified petroleum gas, solvents, or surfactants into the well, usually before the water flooding occurs.
In addition, it has been suggested to use a thermal explosion at the bottom of the well, hopefully to cause additional fissures in the oil bearing formation so as to increase the oil flow. Obviously, thermal explosions have the disadvantage of destroying the well and, also, of having a limited effect if they are to be kept from destroying the well.
In my copending applications Ser. No. 502,661, filed Sept. 3, 1974, and Ser. No. 863,434, filed Dec. 22, 1977, the use of electrohydraulic shock waves generated by capacitor discharge means is disclosed.
It is an object of the present invention to provide a method for recovering oil from an oil bearing formation which is an improvement beyond that disclosed in my copending applications.
It is a further object of the present invention to provide a method which can be easily and efficiently carried out in a well with a minimum of shut down time of well operations.
It is another object of the present invention to provide a recovery method which is economical in operation.